The RecordNotFound error message that is raised when using find on an association which has inverse_of defined does not match the error message that is thrown for non-inverse-of associations.
I've changed the error message to stay consistent with the error thrown for find without an
I also removed some variables that were not needed in the test cases related to the RecordNotFound error messages.
Updated the error message for +find+ on an inverse_of association
so that it is consistent with the error thrown for +find+ without an